Hereinafter, where the attachment of a disc to a wheel rim is referred to, it should be understood that the description is also applicable to attachment of a mounting ring to a wheel rim. In demountable rims, the mounting ring is releasably secured to a hub, as is well known.
Manufacturers of wheels historically have chosen to attach the disc of the wheel to the rim of the wheel at a variety of locations. In certain instances, the outer skirt flange of the disc is welded to the rim at the drop center well of the rim. In other instances, the skirt flange of the disc is welded to the rim at the ledge of the rim. In further instances, the skirt flange of the disc has been welded to the angled under surface of the beadseat of the rim, or to a flat under surface of a built up, thickened, area below the beadseat of the rim. Each of these designs represents a compromise of sorts.
When the outer skirt flange of the disc is welded to the rim at the well, the internal space within the rim for vehicle components such as the brake assembly is minimized. This is not a problem where wheel diameter is adequate and internal rim components such as brake assemblies are not overly large. However, current designs of wheels for trucks, trailers, buses, etc. have reduced wheel diameters and larger brake assemblies, but still require sufficient internal clearance between the rim and brake assembly in order that heat from the brake assembly will not excessively dissipate through the rim to affect brake and tire performance and life. Thus, attachment of the disc outer skirt flange to the rim at the well, providing minimal interval space within the rim, can be a less desirable design. Further, a "full contour" appearance for the wheel cannot be obtained; i.e., the view from the outboard side of the wheel shows a discernable seam at the position where the disc outer skirt flange is welded to the rim, and a less aesthetic appearance of the wheel is obtained. "Full contour" is a term in the wheel industry that refers to the front wheel position of the vehicle.
Where the outer skirt flange of the disc is attached to the inflation ledge of the rim, design difficulties remain. The inflation ledge is present in certain rims wherein first and second axially spaced and outwardly angled beadseats are separated by a well and the ledge, generally cylindrical, extending between the first beadseat and the well. Where the outer skirt flange of the disc is welded to the ledge, a "full contour" wheel appearance cannot be obtained, and there may be less interior space within the rim for the brake assembly to have proper heat dissipation which is not excessively transferred to the rim.
Accordingly, numerous wheel designs have seen the attachment of the outer skirt flange of the disc to the under surface of the beadseat, the upper tire-contacting surface of the beadseat being outwardly angled. Where the under surface of the beadseat also is outwardly angled, in a frusto-conical shape, the outer surface of the disc outer skirt flange is also designed with a matching frusto-conical shape so that the two frusto-conical shapes contact each other on assembly and welding of the disc outer skirt flange to the rim. In this design, a "full-contour" appearance wheel can be obtained, and adequate space may be obtained within the rim for the brake assembly to properly dissipate heat. However, other significant problems result. It is difficult to axially position the disc outer skirt flange and the rim upon assembly prior to welding because of the two frusto-conical attachment surfaces being angled with respect to the wheel axis, and because of tolerance angle variations of the two frusto-conical surfaces. A preliminary tack welding operation may be necessary for accurate positioning of the disc flange and rim prior to passing the disc flange and rim to the final welding position in the assembly operation. This results in an additional assembly operation and additional assembly expense. Further and importantly, the disc outer skirt flange and rim, because of the frusto-conical attachment surfaces, cannot be press-fit together prior to welding, thus providing a potentially less secure attachment than that found for example where the rim well or ledge cylindrical surface is attached to the disc skirt flange.
In a still further wheel design, the outer skirt flange of the disc has been attached to the under surface of a beadseat having an outwardly angled upper, tire-contacting surface, with the under surface of the beadseat being built up in a radially inward direction out of additional rim material so that the entire under surface of the material under the beadseat is cylindrical. A "full contour" appearance wheel may be obtained. However, this design does not allow the rim to be made of strip steel without adding additional operations greatly affecting production speed, is very expensive to manufacture out of sectioned steel, and is excessively heavy because of the build up of material under the beadseat.
Examples of the above prior art designs may be found for example within the following: U.S. Pat. Nos. 5,219,441 and 4,504,095; 1974 catalog M-220-44A (Wheels and Rims) of Firestone Steel Products Company, page 7; and German Offenlegungsschrift 1918022.